Welcome to BYC. The crop is in the upper right chest under the neck. It should feel full and soft or have little particles in it in the evening, and by morning, it should be mostly empty before she eats. If it feels very hard it could be impacted, or if it feels puffy and full in the morning, it may be a slow crop or sour crop. A slow crop may occur with an illness or an injury. Sour crop can result from a previously impacted crop, and may cause spitting up of brown foul-smelling liquid. Have you noticed any puffy areas around the neck or chest that could be a leaking air sac from the injury? Antibiotics can be used in chickens that aren't going to be eaten, but it depends on what type of infection there is. Is she having any nasal drainage, gasping, watery eyes, wheezing, or rattles?